This Program provides the biologic models for putative inhibitors using human colon adenocarcinoma cell lines and tumors derived from these cell lines. Past work from my laboratory has demonstrated that activation of pp6c-src and pp62c-yes are consistent in human colon tumors, that activated pp60c-src is important to the tumorigenicity of colon tumor cell lines in nude mice, and that well characterized human colon tumor cell lines such as HT 29 are very useful in screening putative PTK inhibitors. Thus this Program will utilize the systems we have described for screening putative PTK inhibitors developed in the first and second Programs. These screens will include determination of cytotoxicity of the compounds in normal fibroblasts as well as in colon tumor cells, growth inhibition of these cells, and effects on soft agar colony formation. Additionally, this proposal will examine the src kinase activity in inhibited cells to determine that the inhibition corresponds with the predicted mechanism. The program will also perform the tumorigenicity studies at the M.D. Anderson Cancer Center, in hind limb and in orthotopic models for colon cancer in nude mice. Specificity of inhibitors toward pp60c-src will be assessed by examining the effects of the putative PTK inhibitors in rare colon tumor cell lines without activated pp60c-src. In combination with the basic research efforts of my laboratory, this screening will test the hypothesis that a pp60c-src-specific inhibitor will reduce tumorigenicity of model colon tumor cell lines in the absence of significant toxicity. Several lead compounds rare currently at various stages of testing, so each of the various analyses will proceed simultaneously. With the studies of the other Programs in this proposal, we should determine the efficacy of src-specific inhibitors for therapeutic treatment of colon cancer, provide an understanding of the molecular profile of tumors inn which such inhibitors are likely to be affective, and further an understanding of the roles of src family PTKs in colon tumor progression.